1) Field of the Invention
The present invention relates generally to drives for vehicles such as lawn and garden tractors and, more specifically, to thrust washers for axle shafts of such vehicles.
2) Related Art
Lawn and garden tractors typically include drive wheels mounted on keyed axle shafts. The drive wheels or wheel hubs are often free floating on the keyed axle shafts and deliver thrust against the transmission housing in the area around the shafts. A non-rotating washer which engages the transmission housing is placed between the end of the housing and the wheel or wheel hub to protect the axle seal. However, after continued use the washer can wear through and no longer protect the seal. Once the washer is worn through and seal damage occurs, transmission fluid can be lost, resulting in costly transmission failure. One solution to the thrust washer wear problem is to place a second washer on the shaft which rotates with the shaft and bears against the non-rotating washer. Using the two washer approach results in significantly increased washer life. However, keying the second washer to the rotating shaft has proven to be costly because the wheel hubs or wheel bushings have to be machined to provide a mating notch for a tab which projects from the plane of the rotating washer at an angle of about 45 degrees.
It is therefore an object of the invention to provide an improved thrust washer structure for the drive of a vehicle such as a lawn and garden tractor. It is another object of the invention to provide such a structure which overcomes the aforementioned problems.
It is a further object of the invention to provide an improved thrust washer structure for a vehicle drive which includes a fixed washer and a second washer keyed to rotate with the drive axle. It is another object to provide such a structure which has a significantly increased wear life compared to a single washer thrust arrangement but which is relatively inexpensive. It is still another object to provide such a structure which obviates a machining step by eliminating the notch for the projecting tab of the rotating washer.
A thrust washer structure constructed in accordance with the teachings of the present invention includes a first non-rotating washer which bears against the transmission housing. A rotating outer washer is positioned over the axle and includes a tab projecting at a right angle from a portion of the washer face such that the tab engages an existing keyway utilized to transmit drive from the axle to the drive wheel. In the embodiment shown, the tab seats in a keyway located in the wheel hub or bushing.
The thrust washer structure requires no machined notches and instead utilizes an existing keyway, thereby saving manufacturing time and expense. Since an existing keyway is utilized, the rotating keyed washer can be retrofitted to existing products therefore substantially increasing the cost savings. The tab is substantially contained within the keyway to provide a compact arrangement, and the area adjacent the keyway remains relatively unencumbered by additional structure.
These and other objects, features and advantages of the present invention will become apparent to one skilled in the art upon reading the following detailed description in view of the drawings.